Scintillation probe with photomultiplier tube saturation indicator

Abstract

A photomultiplier tube saturation indicator is formed by supplying a supplemental light source, typically an light emitting diode (LED), adjacent to the photomultiplier tube. A switch allows the light source to be activated. The light is forwarded to the photomultiplier tube by an optical fiber. If the probe is properly light tight, then a meter attached to the indicator will register the light from the LED. If the probe is no longer light tight, and the saturation indicator is saturated, no signal will be registered when the LED is activated.

What is claimed is: 
     
       1. A scintillation probe with photomultiplier tube saturation indicator comprising: (a) a light impervious tube with a closed end and an open end for accepting a light pipe;   (b) a photomultiplier tube captured within the light impervious tube between the light pipe and the closed end;   (c) a light source adjacent to the photomultiplier tube;   (d) a switchable power supply connected to said light source wherein the power supply operates independently from the output of the photomultiplier tube; and   (e) a means for measuring the output of the photomultiplier tube when light from the light source is applied to the photomultiplier tube for determining whether the photomultiplier tube is saturated.   
     
     
       2. The scintillation probe of claim 1 further comprising: (f) an optical fiber between said light source and said light pipe.   
     
     
       3. The scintillation probe of claim 1 wherein said light source comprises a light emitting diode. 
     
     
       4. The scintillation probe of claim 1 wherein said switchable power supply comprises a battery connected to a switch wherein said switch is mounted to the closed end of the tube. 
     
     
       5. The scintillator probe of claim 2 wherein the optical fiber and the light source are sealed together with shrink wrap tubing.